/Engine/Source/Runtime/Engine/Classes/GameFramework/SpringArmComponent.h
This function allows subclasses to blend the trace hit location with the desired arm location; by default it returns bHitSomething ? TraceHitLocation : DesiredArmLocation
virtual FVector BlendLocations ( const FVector & DesiredArmLocation, const FVector & TraceHitLocation, bool bHitSomething, float DeltaTime )